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arXiv 1006.0348astro-ph.HEgr-qc
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磁星振荡I:地壳和地核的强耦合动力学

Magnetar Oscillations I: strongly coupled dynamics of the crust and the core

Maarten van Hoven, Yuri Levin

摘要:

在软伽玛中继站观测到的巨耀斑中的准周期振荡通常被解释为磁星的扭转振荡。这种振荡运动受地壳剪切模与地核类阿尔芬模之间的强相互作用的影响。我们研究了通过这种相互作用产生的动力学,并提出了几个新的结果:(1)我们表明,全球{ \it边缘模式}经常居住在附近的核心阿尔芬连续的边缘。(2)我们计算的磁星的振荡运动的现实轴对称磁场配置和核心的密度分布,但与一个简化的模型的弹性地壳。我们表明,一般可以得到多个间隙中的阿尔芬连续。如果地壳频率属于能隙,则得到离散的全局{ \it能隙模}。(3)我们表明,在核心领域纠缠增强的核心离散阿尔芬模式的作用,并减少了核心阿尔芬连续的作用,在整体振荡动力学的磁星。(4)我们表明,该系统显示瞬态和/或漂移QPO的核心阿尔芬模式的频谱的部分时,包含离散的模式是密集和定期间隔的频率。(5)我们表明,如果中子耦合到核心阿尔芬运动,那么耀斑后地壳运动是强烈阻尼,并有一个非常弱的振幅。因此,磁星QPO提供的证据表明,在核心的质子和中子组件动态解耦,其中至少有一个是量子流体。(6)我们表明,这是很难确定的高频625赫兹QPO是由于磁星的物理振荡模式,如果后者的流体核心组成的标准质子-中子-电子的混合物,并磁化到相同的程度作为地壳。(摘要节略)

英文摘要:

Quasi-Periodic Oscillations (QPOs) observed during Soft Gamma Repeaters giant flares are commonly interpreted as the torsional oscillations of magnetars. The oscillatory motion is influenced by the strong interaction between the shear modes of the crust and Alfven-like modes in the core. We study the dynamics which arises through this interaction, and present several new results: (1) We show that global {\it edge modes} frequently reside near the edges of the core Alfven continuum. (2) We compute the magnetar's oscillatory motion for realistic axisymmetric magnetic field configurations and core density profiles, but with a simplified model of the elastic crust. We show that one may generically get multiple gaps in the Alfven continuum. One obtains discrete global {\it gap modes} if the crustal frequencies belong to the gaps. (3) We show that field tangling in the core enhances the role of the core discrete Alfven modes and reduces the role of the core Alfven continuum in the overall oscillatory dynamics of the magnetar. (4) We demonstrate that the system displays transient and/or drifting QPOs when parts of the spectrum of the core Alfven modes contain discrete modes which are densely and regularly spaced in frequency. (5) We show that if the neutrons are coupled into the core Alfven motion, then the post-flare crustal motion is strongly damped and has a very weak amplitude. Thus magnetar QPOs give evidence that the proton and neutron components in the core are dynamically decoupled and that at least one of them is a quantum fluid. (6) We show that it is difficult to identify the high-frequency 625 Hz QPO as being due to the physical oscillatory mode of the magnetar, if the latter's fluid core consists of the standard proton-neutron-electron mixture and is magnetised to the same extent as the crust. (Abstract abridged)

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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